Interesting:

All of the Match/Varmint Grade 40-XBs, regardless whether single shot, or repeater, are marked (Stamped!) 40-X on the left side of the receiver, opposite of the ejection port. The "B" part of the designation is the last digit of the serial number, as in "XXXXXX B".

There are NO match rifles marked "40-XB".


http://www.snipercountry.com/Articles/Remington40X.asp